Often, a blood processing or apheresis instrument is used to separate blood components from whole blood. Such apheresis instruments are commercially available from various sources, including the Amicus® instrument which is available from Fenwal Inc., of Lake Zurich, Ill. Such instruments, also known as “separators”, typically separate a selected blood component from whole blood by passing the blood of a donor through the instrument to separate one or more blood components from the whole blood. The remainder of the whole blood is then returned to the circulatory system of the donor. It is, therefore, an extracorporeal blood component collection process.
Instruments such as the Amicus instrument may utilize a disposable apheresis kit for collection of a desired blood component. The instrument may have pumps, clamps, and valves that move and direct donor blood through the kit. Such kits are often referred to as “disposables”. Connected to such a kit may be one or more fluid supply containers of replacement fluids for infusion into the donor. Indeed, a therapeutic plasma exchange (TPE) procedure may require multiple containers of fluid to replace potentially up to three or more liters of the patient's waste plasma.
During an apheresis procedure, one of the most significant concerns is prevention of an air embolism. To reduce the risk of air embolism, it is vital to ensure that air does not enter the apheresis disposable kit during a blood component collection procedure. For example, air can be drawn into the disposable kit during a collection procedure when the fluid source, or fluid supply container attached to the kit becomes exhausted of fluid.
During therapeutic plasmapheresis, a patient's plasma is continuously removed while normal plasma or albumin (replacement fluid) is continuously infused. In current practice, two replacement fluid supply containers are usually connected to the disposable kit. Replacement fluid is drawn from one container while the other container is clamped. The operator must closely monitor the fluid level in the “active” container. When this container empties, the operator must close its clamp while opening the clamp on the other container. If the operator is occupied with the patient, or otherwise distracted, and does not perform this operation, a large volume of air may be drawn into the disposable kit, requiring air to be purged.
Apheresis instruments are typically equipped with air detection systems that continually monitor the fluid that is being returned to the donor/patient. If, during a procedure, air reaches the air detection system, blood processing is interrupted until the air is purged from the system. Often multiple air purges are required to clear this air. Since blood is not being processed during these purges, the overall efficiency of the blood collection procedure is decreased.
A general object of the present disclosure is to therefore provide apparatus and methods for automatically determining when a fluid container becomes empty and to terminate further use of the empty container.
Another object of the present disclosure is to provide apparatus and methods for determining when a fluid container becomes empty independent of the size, volume or composition of matter of the container.
A further object of the present disclosure is to provide a system for determining when the rate of change of the weight of the container and its fluid is less than expected.
Yet another object of the present disclosure is to automatically begin pumping from a second container when it is determined that a first container is empty.
A still further object of the present disclosure is to provide apparatus for determining when a fluid container becomes empty independent of flow rate from the container.